Pakistani security officials examine the site of a bombing on an entrance of a hospital in Dera Ismail Khan, Pakistan, Sunday, July 21, 2019. Police in Pakistan say gunmen opened fire on a police post and then bombed the entrance to a hospital as the wounded were being brought in. (AP Photo/Ishtiaq Mahsud)

Islamabad - At least seven people, including four policemen, were killed in twin attacks in north-western Pakistan on Sunday, officials said.

In the first incident, gunmen opened fire at a police checkpoint in the city of Dera Ismail Khan and killed two officers.

A suicide bomber then blew themselves up outside a hospital gate as the ambulance carrying the two officers arrived.

City police spokesman Arshad Ali said at least five people were killed in the second attack, including two policemen. Another 17 people were wounded.

Ali said it was not yet clear whether the suicide bomber was male or female, although there were early indications that a woman carried out the blast.

A bomb disposal squad and other investigative agencies were collecting evidence while a search and clearance operation in the area was under way, he said.

No group has yet claimed responsibility.

The Pakistani military has pushed Islamist militants back from their mountainous hideouts in north-western Pakistan near the Afghan border in a series of offensives launched from mid-2014.

However, the their capability to launch attacks on soft targets or the civilian population remains intact, posing a security challenge.

Last month, the army said that terrorist activity had jumped in the tribal region bordering Afghanistan and at least 10 members of the security forces had been killed and 35 injured over the past months.